1. Field of the Invention
The present invention relates to a new vector system to facilitate the cloning and functional analysis of new genes of a fly, Drosophila melanogaster, and a method for gene trapping with the vector system.
2. Description of the Related Art
There are numerous examples for application of gene trapping methods in wide range of living organisms including maize and mouse (Gossler et al,. Science, 244:463–465, 1989).
With respect to tools for gene trapping, the application of different types of enhancer trap P-element vectors (Wilson et al., Genes & Development, 3:1301–1313, 1989) for cloning and analyzing trapped genes, as well their use for mosaic analysis with the help of the Gal4/UAS transcription activator system has proven fruitful. However, sometimes the expression pattern of the Gal4 or other reporter gene of the vector construct is affected by enhancers belonging to more than one gene. Similarly, in some cases it is difficult to determine whether the enhancer trap insertion effects the function of one or more of the neighboring genes.
These circumstances altogether with the fact that in some cases the mutant phenotype could be attributed to the changed expression of a gene with its nearest exon located more than 30 kB apart from the insertion site, can lead in unfortunate cases to an ordeal when it's time to clone and analyze the affected gene.
One object of this application is to provide a vector system that includes specifically designed artificial regulatory sequences as well as selection methods for easy screening of positive recombinant lines. More especially, this application intends to provide a vector system of this invention offering much easier and faster cloning opportunities of the affected gene, compared to the widely used enhancer trap P-element vectors. Another object of this application is to provide easier detection method possibilities of the successful trapping events and much higher chance to get more characteristic (“functional”) expression patterns of the reporter gene because in the contrary with much of the cases with enhancer trap lines, when using the vector system of this invention, the reporter gene expression is influenced only by a single endogenous transcription unit and effects only the expression of the very same gene.